Broken springs on a tractor trailer present a serious hazard to the drivers of such vehicles. When a spring breaks on a loaded trailer, the frame of the trailer drops directly onto the tires, requiring immediate repair. If this occurs during operation of the vehicle, it may result in an accident because the load of the trailer drops directly onto the rotating wheels and also shifts within the trailer. A broken spring on the trailer requires immediate repair. Because the load has dropped onto the tires, a broken spring usually renders the vehicle immovable.
Various arrangements of suspension known to the prior art seek to equalize the displacement of a trailer load by the use of various rubber or elastomeric materials incorporated within the suspension system. Known devices generally attempt to supplement the existing spring system of a vehicle suspension by providing elastomeric material or mats positioned at various locations within the trailer subframe for the purpose of equalizing the displacement of the load within the trailer while the trailer is being driven around curves or over bumps in the road. Other known arrangements seek to replace all springs in a trailer suspension by only various elastomeric elements or materials. Typical examples of the use of elastomeric or rubber materials in a vehicle suspension can be found in the following United States patents: U.S. Pat. No. 1,071,517; U.S. Pat. No. 1,850,259; U.S. Pat. No. 1,869,137; U.S. Pat. No. 2,110,583; U.S. Pat. No. 2,167,911; U.S. Pat. No. 2,199,896; U.S. Pat. No. 2,280,347; U.S. Pat. No. 2,612,369; U.S. Pat. No. 2,661,943; U.S. Pat. No. 2,715,041; U.S. Pat. No. 2,929,618; U.S. Pat. No. 2,951,709; U.S. Pat. No. 3,089,690; U.S. Pat. No. 3,528,680; U.S. Pat. No. 3,606,376; U.S. Pat. No. 3,642,302; U.S. Pat. No. 3,850,444; U.S. Pat. No. 3,895,819; U.S. Pat. No. 3,927,907; U.S. Pat. No. 3,970,162; U.S. Pat. No. 4,029,335; and U.S. Pat. No. 4,272,101.
It is the object of the present invention to provide a spring suspension system for a trailer which includes a resilient mat formed from elastomeric material which is positioned on the trailer subframe so as to both supplement the spring action of the trailer springs under a heavy load, and also to act as an auxiliary suspension system to prevent the trailer subframe from dropping onto the trailer tires in the event the primary supporting springs break for the purpose of maintaining the trailer in movable and drivable condition even after the trailer springs have ruptured.